ZFS, the space-age filesystem developed by Sun, is now available for Mac OS X Leopard. You can get the binaries and source code from ZFS on OS X. Be warned that this is a beta version fun for testing and learning but not ready for mission-critical systems.
ZFS, all by itself, replaces the herd of separate filesystem management tools we've come to rely on: fsck, dump, restore, mkfs, tunefs, volume managers like EVM and LVM, raidtools, mdadm, rysnc, quota, fdisk, and all the rest. Mac OS X uses HFS+, which is a perfectly good journaling filesystem. However, it's not in the same class as ZFS. This is not meant as a criticism, as very few filesystems are.
You can't have your root filesystem using ZFS, but if you have a large enough hard disk you can test all of its features, including pools and simple RAID setups. Don't do anything to the partition containing your root filesystem, and remember that every partition ZFS touches will be overwritten.
diskutil list displays your existing partitions. Creating a ZFS-formatted storage pool with two disk partitions is done like this:
# zpool create newpool /device1 /device2
# zpool create newmirror mirror /device1 /device2